Generally, a melt conjugated spinning apparatus is a spinning machine wherein different kinds of polymer materials are introduced into two or more melt extruders, melted with heat and pressure, and added in a pack having a plurality of distribution plates and nozzles to a desired fiber section and shape.
The fiber made by the melt conjugated spinning apparatus is called a conjugated fiber, and since the conjugated fiber is made through the conjugated spinning with different kinds of polymer materials, the conjugated fiber has core-sheath type, side-by-side type, and sea-island type cross sections.
Further, fibers having different physical properties (strength and elongation), thicknesses and sectional shapes (circular, +, Y, −, and hollow shapes) are made of the same kind or different kinds of polymer materials through the melt conjugated spinning apparatus, and next, the fibers are added in post process. In this case, the fibers are called blended yarn (blended fibers).
In case of the blended yarn, different fibers are made individually, and they are then added to each other in the post process, thus undesirably making the manufacturing process complicated, decreasing the productivity, and increasing the manufacturing cost. Above all, the conventional melt conjugated spinning apparatus does not manufacture the multiple conjugated yarn made of three or more kinds of polymer materials, thus undesirably causing various functions and properties of the polymer materials to be restrictedly expressed.
Accordingly, Korean Patent Application Laid-Open No. 2012-52722 as filed by the same inventors as the invention discloses a multiple fiber spinning apparatus wherein multiple kinds of polymer materials are spun at the same time to manufacture the fiber yarn having various internal structures. As a result, the multiple kinds of polymer materials are spun at the same time from the apparatus, thus obtaining the multiple composite or blended fiber having various functions and performance.
Generally, paper used as sheets for bank money, check, passports, bonds, marketable securities and so on requiring security makes use of fluorescent yarn having counterfeit prevention effects, visual effects, and authenticity identification effects, and accordingly, the fluorescent yarn as synthetic fibers added to the paper to a small number is called security yarn.
Generally, staple fibers having 3 to 10 mm are partially colored or fluorescent, and next, they are added during a paper making process of perfect stuff to provide visually different colors or a fluorescent color under ultraviolet rays, thus making a difference from general paper.
Objects of recent security elements are to provide an identification capability by naked eyes and to provide an authentication capability through an identifier. That is, it is necessary to perform rapid and clear authentication through machines because of deposit and withdrawal of marketable securities by automated teller machines, the use in automatic vending machines, and the distribution of various security products.
Conventional fluorescent yarn is disclosed in Korean Patent No. 346056, wherein the fluorescent yarn has a single color made by mixing a fluorescent pigment with a synthetic resin and by melt spinning the mixed material. Another fluorescent yarn used for a security film is disclosed in Korean Patent No. 374293, wherein red, blue and green fluorescent pigments are dyed with nylon yarn by color to make fluorescent yarn having a single color like red, blue and green expressed on each strand, and next, the fluorescent yarn having different colors is mixed. However, the conventional fluorescent yarn has a simple color or structure and a low degree of uniformity in color upon dyeing, thus exhibiting a bad counterfeit prevention capability.
So as to remove the above-mentioned problems, there have been various technologies for the visual effects of the fluorescent yarn, and one of the conventional technologies is disclosed in Korean Patent Gazette No. 1996-1336 wherein there is provided a method for manufacturing a fiber having different colors or multiple colors dyed with two or more pigments thereon. That is, the fiber is primarily dyed, while portions of the fiber spaced apart from each other by given distances are being shielded, and then, the fiber is dried. Next, the shielded portions are open, while the dyed portions are being shielded, and they are dyed with different color from the primarily dyed color. Further, Korean Patent No. 259825 discloses a method for manufacturing a multi-colored fiber wherein a plurality of fibers is dyed on the exposed portion thereof in the state of being twisted, and next, after the fibers are cut and untwisted from the twisted state, the portions not exposed to the outside are dyed with different colors from the colors first dyed. According to the conventional methods, however, the dyeing process becomes complicated, and it is hard to manufacture the fluorescent yarn in large quantities. Further, the boundary surface between the dyed portions is not uniform, and the dyeing is conducted on the surface of the fiber, thus making the durability deteriorated.
On the other hand, U.S. Pat. No. 4,655,788 discloses a method for manufacturing fluorescent yarn having fluorescent material excited on infrared rays, visible light, and ultraviolet rays, wherein two materials excited on different light sources are provided to reduce the possibility of counterfeit.
Accordingly, the present inventors have made various studies to solve the above problems and as a result, they have found that if a multi-component spinning fiber is applied to security yarn and components identified by wavelength are contained in at least one or more kinds of polymer materials, a multi-identification capability can be provided. It has been further found that if the whole specific gravity of the security yarn containing the multi-component spinning fiber satisfies more than 1, the security yarn is submerged upon a paper making process, thus increasing the contents thereof, and if a hydrophilic polymer material is located as an outer component of the multi-component spinning fiber, the dispersion rate in water of the security yarn is improved and the mixing with perfect stuff is advantageously conducted during the paper making process, thus enhancing the identification efficiencies of security products using the security yarn providing the multi-identification capability.